JPH0429074Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an exhaust gas recirculation device for a diesel engine.

(Prior Art) Conventionally, an exhaust recirculation device using an intake throttle valve has been known for an engine, which recirculates a portion of intake gas to the intake system through an exhaust recirculation passage to reduce _NOx . For example, Akira Jitsukai
As described in Japanese Patent No. 55-100052, there is a device that controls the opening and closing of the intake throttle valve using a diaphragm device that controls the opening and closing of the intake throttle valve based on the differential pressure between the pressure downstream of the intake throttle valve and atmospheric pressure.

In such an exhaust recirculation device, when an exhaust recirculation valve is installed in the middle of the exhaust recirculation passage in order to perform exhaust recirculation control accurately, the exhaust gas is Since carbon and other substances adhere to the exhaust gas and change its opening area, it is possible to use an ON-OFF type exhaust recirculation valve that can be switched between fully open and fully closed positions to reduce the effect of this change. .

(Problem to be solved by the invention) However, when doing so, the pressure downstream of the intake throttle valve changes significantly when the exhaust recirculation valve is switched from the fully closed position to the fully open position, and this change in pressure causes the intake throttle valve to change significantly. Since the opening degree is controlled, there is a risk that the exhaust gas recirculation rate will become excessive and the combustibility will deteriorate.

The present invention has been developed in view of these points, and is a diesel engine that prevents the abnormal increase in the exhaust recirculation rate that may occur when switching the exhaust recirculation valve from the fully closed position to the fully open position, thereby preventing deterioration of combustibility. The purpose is to provide an exhaust gas recirculation device.

(Means for Solving the Problems) The present invention includes an exhaust recirculation passage that connects an exhaust passage and an intake passage of an engine, and an exhaust recirculation passage that is interposed in the exhaust recirculation passage and is controlled to be switched between a fully open position and a front close position.
An ON-OFF type exhaust recirculation valve and an intake throttle valve disposed in the intake passage upstream of the downstream end opening of the exhaust recirculation passage, and when the engine is under low load, the intake passage downstream of the intake throttle valve is provided. In an exhaust recirculation system for a diesel engine configured to control the opening degree of an intake throttle valve according to the internal pressure of the intake throttle valve to a set opening degree based on a required exhaust gas recirculation amount, the exhaust gas recirculation valve The present invention is characterized in that a correction means is provided for correcting the intake throttle valve from the set opening degree to the predetermined opening direction for a predetermined period of time after the switching from the fully closed position to the fully open position.

(Function) With the correction means, when the ON-OFF type exhaust recirculation valve is switched from the fully closed position to the fully open position during low engine load, the intake throttle valve is adjusted to maintain the required exhaust level for a predetermined period of time after the switching. The set opening based on the recirculation amount is corrected toward a predetermined opening, thereby preventing an abnormal increase in the exhaust gas recirculation rate.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 and 2, 1 is an indirect injection type four-cylinder diesel engine, 2 is a combustion chamber of each cylinder 3, 4 is an intake passage, and a main intake passage 5.
The combustion chamber 2 of each cylinder 3 is branched from the main intake passage 5.
It consists of four branch intake passages 6 communicating with each other, and each intake passage 6 is provided with an air heater 7 for heating intake air.

Reference numeral 8 denotes an intake throttle valve, whose opening and closing are controlled by a diaphragm device 9. In the diaphragm device 9, a casing 9a is divided into a first chamber 9c and a second chamber 9d by a diaphragm 9b. 1st
A negative pressure passage 11 in which a spring 9e is compressed and a negative pressure control solenoid valve 10 is interposed is connected to the chamber 9c. Also, diaphragm 9
b is linked to the intake throttle valve 8 via a link mechanism 9f extending toward the second chamber 9d.

The intake throttle valve 8 has, for example, an engine cooling water temperature (hereinafter simply referred to as water temperature) of 30 to 60°C, an engine load (hereinafter referred to as average effective pressure Pe) of 1 kg/cm ² or less,
In addition, the intake negative pressure is controlled to improve the heating efficiency of the air heater 7 in a region where the engine speed is 2000 rpm or less.

12 is an exhaust gas recirculation passage (hereinafter referred to as EGR passage)
The exhaust passage 13 is connected to the intake passage 4 downstream of the intake throttle valve 8. Therefore, the intake throttle valve 8
is disposed in the intake passage 4 upstream of the downstream end opening of the exhaust gas recirculation passage 12.

A blocking wall 16 having a large diameter hole 14 and a small diameter hole 15 is interposed in the middle of the EGR passage 12, and first and second exhaust recirculation valves 17 close both holes 14 and 15 of the blocking wall 16. , 18 (hereinafter referred to as the EGR valve) are provided. 1st and 2nd EGR valve 1
7 and 18 each have a fully open position and a fully closed position, and when the first EGR valve 17 is in the fully open position, the large diameter hole 14 is open, and when the second EGR valve 18 is in the fully open position, the small diameter hole 15 is open. and the first
1When the EGR valve 17 is in the fully open position, the
2 EGR than when the EGR valve 18 is in the fully open position.
It is structured to increase the amount.

Each EGR valve 17, 18 has a casing 17a,
18a is divided into first chambers 17c, 18c and second chambers 17d, 18d by diaphragms 17b, 18b, and a spring 17 is provided in the first chambers 17c, 18c.
e, 18e are compressed, and a negative pressure passage 21 in which negative pressure control solenoid valves 19, 20 are interposed;
22 is connected, and rod members 17f, 1 are connected to the second chambers 17d, 18d of the diaphragms 17b, 18b.
Valve bodies 17g and 18g that open and close the holes 14 and 15 are connected via 8f.

The first and second EGR valves 17 and 18, together with the intake throttle valve 8, are operated, for example, at a water temperature of 60 to 100°C, an engine load of 6 kg/cm ² or less, and an engine speed of 900 to 900.
It is controlled according to the engine load as follows in the range of 3000 rpm and 1st to 4th speed (for a 5th speed car).

When the engine load is 5 to 6 kg/cm ² ...
The first EGR valve 17 is closed, the second EGR valve 18 is open, and the intake throttle valve 8 is fully open.

When the engine load is 4.5 to 5 Kg/cm ² ...
The first EGR valve 17 is open, the second EGR valve 18 is closed, and the intake throttle valve 8 is fully open.

When the engine load is 0 to 4.5Kg/ ^cm2 ...
The opening degree of the intake throttle valve 8 is controlled by opening the first EGR valve 17 and closing the second EGR valve 18.

If the engine load is 0Kg/ ^cm2 or less...
The first EGR valve 17 is closed, the second EGR valve 18 is closed, and the intake throttle valve 8 is opened at a constant degree.

25 is an intake pressure sensor disposed in the intake passage 4 and detects the intake pressure; 26 is a control unit that controls the operation of the engine 1; In addition to being electrically linked, detection means (not shown) indicates a water temperature signal corresponding to the engine cooling water temperature, a rotation signal corresponding to the engine rotation speed, a load signal corresponding to the engine load, and 5 indicating whether or not the engine is in the 5th gear position. The speed switch signals are respectively input.

The control unit 26 includes an intake air heating region determining means 101 and an exhaust recirculation region determining means 10.
2, an air heater control means 103, an intake throttle valve control means 104, an EGR valve control means 105, and a correction means 106.

Then, based on the water temperature signal, the rotation signal, and the load signal, the intake air heating region determining means 101 determines whether or not it is in the intake air heating region.
Air heater control means 1 based on the output signal from 01
At step 03, the air heater 7 is controlled, and the intake throttle valve 8 is controlled by the intake throttle valve control means 104.

On the other hand, water temperature signal, rotation signal, load signal and 5
Exhaust recirculation region determination means 10 based on the speed switch signal
2, it is determined whether or not the exhaust gas recirculation region is present, and the intake throttle valve 8 is controlled by the intake throttle valve control means 104 according to the rotation signal and the load signal based on the output signal from the exhaust gas recirculation region determination means 102. However, the EGR valves 17 and 18 are controlled by the EGR valve control means 105, respectively. As described later, when the engine is under low load, the opening degree of the intake throttle valve 8 is controlled according to the pressure in the intake passage 4 downstream of the intake throttle valve 8, and the opening degree is controlled based on the required exhaust gas recirculation amount. It has come to be controlled by

At the same time, the exhaust recirculation region determining means 10
The correction means 106 switches the EGR valves 17 and 18 (in this embodiment, the first EGR valve 17
When the EGR valve is switched from the fully closed position to the fully open position during low engine load, the intake throttle valve 8 is moved from the set opening to the specified opening direction for a set time after the switching. It is now being corrected.

Although the fuel injection pump is not shown,
The advance angle is controlled by the control unit 26 as follows.

Water temperature below 30℃, engine load below 0Kg/ ^cm2 ,
Engine speed 2000rpm or less and intake temperature 10℃
In the following areas, the advance angle is controlled according to water temperature, rotation speed, and intake air temperature.

In each water temperature range of 30 to 60℃ and 60 to 100℃, engine load is 6Kg/cm2 ^or less, engine rotation speed is 900 to 3000rpm, intake temperature is 10℃ or more, and 1 to 10℃.
In the 4th gear (for 5th gear vehicles) range, advance angle control is performed according to the load and rotation speed.

In areas other than the above, advance angle control is performed according to the engine speed.

Next, the control operation of the control unit 26 will be explained with reference to FIGS. 2 to 4.

First, in step S1, the water temperature sensor (not shown) is
The water temperature signal is input, and the water temperature is determined in step S2.
It is determined whether the temperature is below 60°C, and if YES, the process moves to step S3; if NO, the process moves to step S4.

In step S3, a rotation signal is input, and in step S5, it is determined whether the engine rotation speed N is 2000 rpm or less. If YES, the process moves to step S6, while if NO, the process returns to step S1. In step S6, a load signal is input, and in step S7, it is determined whether the engine load Pe is 1 kg/cm ² or less. If YES, it is in the intake air heating region, so
Turn on the air heater 7 in step S8, and then turn on the air heater 7 in step S9.
~ In S12, intake air heating control is performed, while in the case of NO, the process returns to step S1. In the intake air heating control, first, in step S9, the set opening degree θm of the intake throttle valve 8 is read from the intake air heating control map M1 (see Fig. 3a) according to the engine speed N, and in step S10, the set opening degree θm is read. Negative pressure control solenoid valve 1 according to degree θm
0 is duty-controlled, a negative pressure signal corresponding to the intake pressure is inputted from the intake pressure sensor 25 in step S11, and it is determined in step S12 whether or not the opening degree θ corresponding to the intake pressure is equal to the set opening degree θm. , if YES, return to step S1; if NO, return to step S1.
By returning to S10, feedback control is performed until θ=θm.

Further, in step S4, it is determined whether the water temperature is 100°C or less, and if YES, the process moves to step S13, while if NO, the process returns to step S1. In step S13, the 5th speed switch signal is input, and in step S14 it is determined whether the speed is 1st to 4th, and YES.
If YES, the process moves to step S15, while if NO, the process returns to step S1.

In step S15, a rotation signal is input, and in step S16, it is determined whether or not the engine rotation speed N is within the range of 900 to 3000 rpm.If YES, it means that the load is low, and the process moves to step S17, while NO If so, return to step S1.

In step S17, a load signal is input, and in step S18, it is determined whether the engine load Pe is within the range of 0 to 4.5 kg/ ^cm2 . If YES, the process advances to step S19, and if NO, the process advances to step S19. Move to S20.

In step S19, the first EGR valve 17 is turned on to switch from the fully closed position to the fully open position, and in step S21, the intake throttle valve 8 is turned on based on the exhaust recirculation control map M2 (see Fig. 3b) according to the engine load and engine speed.
Read the set opening degree θM and start the 1st EGR in step S22.
It is determined whether the elapsed time t after switching the valve 17 from the fully closed position to the fully open position is less than or equal to a certain time T, and if YES, the exhaust gas recirculation is adjusted using a correction coefficient for the duty ratio in step S23. In order to prevent an abnormal increase in the ratio, the opening of the intake throttle valve 8 is corrected in the opening direction to a corrected opening θM', and in step S24, the duty of the intake throttle valve 8 is controlled by the negative pressure control solenoid valve 10. , a negative pressure signal is input in step S25, and the opening degree θ corresponding to the intake pressure is determined in step S26.
It is determined whether or not is equal to the corrected opening degree θM', and if YES, the process returns to step S1, while if NO, the process returns to step S24 to perform feedback control. On the other hand, if NO in step S22, the process moves to step S27, where normal duty control is performed on the intake throttle valve 8, a negative pressure signal is inputted in step S28, and the opening degree θ corresponding to the intake pressure is input in step S29. Determine whether or not is equal to the set opening degree θM. If YES, proceed to step S1; if NO, return to step S27.
Feedback control is performed until θ=θM.

Also, in step S20, the engine load Pe is 4.5.
It is determined whether it is within the range of ~5Kg/ ^cm2 ,
If YES, turn off the first EGR valve 17 in step S30.
ON, the intake throttle valve 8 is fully opened in step S31, and the process returns to step S1.
Move to.

At step S32, the engine load Pe is 5 to 6 kg/
It is determined whether or not it is within the range of cm ^2. If YES, the second EGR valve 18 is turned ON in step S33, the intake throttle valve 8 is fully opened in step S34, and the process returns to step S1. Since this is not the exhaust gas recirculation region, the process immediately returns to step S1.

(Effects of the invention) As described above, the present invention has the advantage that when the exhaust recirculation valve of the ON-OFF type is switched from the fully closed position to the fully open position during low engine load, the intake air is throttled for a predetermined period of time after the switching. Since the valve is corrected to a predetermined opening direction from the set opening based on the required exhaust recirculation amount, an abnormal increase in the exhaust recirculation rate that may occur when switching the exhaust recirculation valve from the fully closed position to the fully open position is prevented. This makes it possible to prevent deterioration of combustibility.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is an overall configuration diagram of an exhaust gas recirculation system for a diesel engine, Fig. 2 is a flow chart showing the processing flow of the control unit, and Fig. 3 a and b are illustrations of the intake air recirculation system. FIG. 3 is a diagram showing control maps for heating and exhaust gas recirculation. 1... Diesel engine, 4... Intake passage,
8...Intake throttle valve, 12...Exhaust recirculation passage (EGR
passage), 13...Exhaust passage, 17, 18...Exhaust recirculation valve (EGR valve), 25...Intake pressure sensor, 26
...Control unit, 106...Correction means.

Claims (1)

[Scope of claim for utility model registration] Exhaust recirculation passage that connects the exhaust passage and intake passage of the engine, and an ON-OFF type exhaust recirculation that is interposed in the exhaust recirculation passage and is controlled to switch between a fully open position and a front close position. and an intake throttle valve disposed in an intake passage upstream of the downstream end opening of the exhaust gas recirculation passage, and the intake throttle valve is configured to control the intake air according to the pressure in the intake passage downstream of the intake throttle valve when the engine is under low load. In an exhaust gas recirculation system for a diesel engine configured to control the opening degree of a throttle valve to a set opening degree based on a required exhaust gas recirculation amount, the exhaust gas recirculation valve changes from a fully closed position to a fully open position when the engine is under low load. 1. An exhaust gas recirculation system for a diesel engine, comprising a correction means for correcting an intake throttle valve from a set opening degree to a predetermined opening direction for a predetermined period of time after the switching.